Amazon Trade-In Video Games

I have the Wii, as the majority of people do. I don't buy many games, b/c really, I just like the active ones. Wii Sports; Wii Fit; Guitar Hero and my favorite at the moment; Just Dance! Back for my birthday my brother asked me what I wanted, so I told him a Wii game that will stimulate my mind. A few days later I got Big Brain Academy; Wii Degree in the mail. I played it a bunch and started to get good at it (except the math) so I took it out of the console, never to look back. I felt like I've conquered it, now it's time to move on. Once I got the Wii Fit and the balance board, I wanted to venture out and play games with it, so I bought Wii Ski. This game was nothing like I expected, and I actually never mastered it, b/c I thought it was annoying. So this came out of the console, never to return.
Now it's February 2010 and Wii Fit came out with a Plus edition. I'm curious. I started to search the web, where can I buy it, how much, and what do people have to say about it. I stumbled upon it on Amazon, and noticed in the left hand column there was a link to the Amazon Trade-In Program. I started to search away on the two games above. I found out I could get $6.50 and $6.00 back for both games. This made my wheels start turning... if i get $12.50 back for trading in 2 Wii games and Wii Fit Plus was going for $19.96, then I can basically pay less then $8 for a new Wii game. Now this I like. I decided to check the trade in value of Wii Fit Plus (just in case I'm not impressed), and found out I can get $16 for it. Pretty good deal if you ask me. I'm still trying to figure out how the value is determined. Must have something to do with how much it is going for on Amazon. Anyways, today I decided to submit my trade ins and sent them off in the mail via free shipping thru UPS. I had to chase the UPS guy outside because I just missed him in the office. Off they go... now I will just wait patiently (probably impatiently) for my games to be approved as "in good condition" by a third party of Amazon before my $12.50 credit show up in my Amazon account.
If you want more info about the trade in program, check this link out. http://www.amazon.com/Video-Games-Trade-In/b/ref=sv_vg_0?ie=UTF8&node=979418011